Anodizing is an electrochemical process that thickens a naturally occurring protective oxide on a metal surface. An anodizing process involves converting part of a metal surface to an anodic film. Thus, an anodic film becomes an integral part of the metal surface. Due to its relative hardness, an anodic film can provide corrosion resistance and wear protection for an underlying metal. In addition, an anodic film can enhance a cosmetic appearance of a metal surface. For example, anodic films can have a porous microstructure that can be infused with dyes to impart a desired color to the anodic films.
Conventional methods for coloring anodic films, however, have not been able to achieve an anodic film with an opaque and saturated white appearance. In particular, the underling metal substrate can often be seen through the anodic film such that the anodized substrate appears to have a silver or metallic appearance. Thus, conventional techniques result in films that appear to be off-white or have a grey or silver hue. What is needed are improved methods for forming white appearing anodic films.